What is the rate of coronary occlusion in out of hospital cardiac arrest (OHCA)?
We know that only 30% of patients having an OHCA have ST elevation myocardial infarction (STEMI) on their ecg. In those patients with a Non-STEMI, up to 30% will have coronary artery occlusion (1-3). How do we make sense of it all?
We would assume that the ECG following ROSC may show significant changes of ischaemia. Can we use this initial ECG to predicting STEMI, given that false positive signs of ischaemia may be present, due to low or no flow, during the arrest?
The message in this study, is that we should perhaps wait, before activating the cath lab. The question is; How long do we wait? Read on to find the answer.
The Study:
The Post-ROSC Electrocardiogram After Cardiac Arrest (PEACE) Study.
Baldi E., et al. Association of Timing of Electrocardiogram Acquisition After Return of Spontaneous Circulation With Coronary Angiography Findings in Patients With Out-of-Hospital Cardiac Arrest. JAMA Network Open. 2021;4(1):e2032875.doi:10.1001/jamanetworkopen.2020.32875
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What They Did?
This was a retrospective, multicenter cohort study conducted at 3 centres ( Italy, Switzerland and Austria), of adult patients who had received resuscitation for OHCA. Only patients with a post-ROSC ECG who underwent coronary angiography were included.
Patients were divided into 4 groups:
- True-positive ECGs: Post-ROSC ECG met STEMI Criteria and had obstructive coronary artery disease on angiography, requiring PTCA.
- True negative ECGs: Post-ROSC ECG did not meet STEMI criteria and there was no obstructive coronary artery disease demonstrated on coronary angiography.
- False-positive ECGs: Post-ROSC ECG met STEMI criteria but did not have obstructive coronary artery disease on angiography.
- False-negative ECGs: Post-ROSC ECGs with no STEMI criteria but with obstructive coronary artery disease on angiography.
N = 370
The ECGs were then analysed for review at 3 time periods: < 7 minutes, 8-33 minutes and > 33 minutes
What They Found
There was a significant decrease in false positive ECGs over time:
- < 7 minutes: 18.5% false positives
- Specificity was 41%
- Positive predictive value for the need for PTCA was 75.3%
- 8-33 minutes: 7.2% false positives
- Specificity was 75%
- Positive predictive value for the need for PTCA was 85.5%
- > 33 minutes: 5.8% false positives.
- Specificity was 81.6%
- Positive predictive value for the need for PTCA was 83.7%.
The conclusion of this study was to wait for 8 minutes before performing a post-ROSC ECG.
The Verdict
This was a retrospective study, and has the limitations that many retrospective studies have.
Some of the limitations that the authors cite, including the diagnosis of STEMI being made on ECG, rather than more advanced techniques, I don't see as a limitation. I see this as reflecting true clinical practice. When you and I assess the patient in the acute situation of a post-ROSC scenario, we make the diagnosis based on the ECG.
The authors recommend that we wait for 8 miutes post-ROSC before performing an ECG. I understand why they recommend this, however I would obtain the ECG as soon as possible. In this study the positive predictive value of the ECG at < 7 minutes was 75.3%. This is still a significant number. The reality, is that with everything that is happenning in that post-ROSC period, it will probably be 8 to 10 minutes before an ECG is done, unless we see ST elevation on the monitor.
I would definitely call cardiology with the intitial ecg, if it showed a STEMI, regardless of when done and allow them to make the decision on angiography. If they decide against it, then serial ECGs are the key. with timing of 15-30 minutes following being optimal.
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References
- Spaulding CM, et al. Immediate coronary angiography in survivors of out-of-hospital cardiac arrest. NEJM 1997;336:1629–33.
- Noc M, et al. Invasive coronary treatment strategies for out-of-hospital cardiac arrest: a consensus statement from the European Association for Percutaneous Cardiovascular Interventions (EAPCI)/Stent for Life (SFL) groups. EuroIntervention: J EuroPCR Collaboration Working Group Interventional Cardiol Europ Soc Cardiol 2014;10:31–7.
- Kern KB, et al. Outcomes of comatose cardiac arrest survivors with and without ST-segment elevation myocardial infarction: importance of coronary angiography. JACC Cardiovascular Interventions 2015;8:1031–40.
